ABSTRACT Hypertension is a complex condition that affects 40% of persons over the age of 25 years. Reduction in blood pressure has been associated with a significant decrease in both coronary heart disease and stroke. Our long term goal is to develop novel therapeutic strategies for hypertension in the context of the cytochrome P450 system. Cytochrome P450 (CYP) 4A11 is an ?-hydroxylase that catalyzes the oxidation of arachidonic acid (AA) to 20-hydroxyeicosatetraenoic acid (20-HETE). 20-HETE can be pro-hypertensive by constricting microvasculature or anti-hypertensive by inhibiting salt reabsorption in the kidney. Thus, 20-HETE and CYP4A11 have important roles in blood pressure regulation. In humans, a genetic variant of CYP4A11 (rs1126742 T8590C allele) encodes for a protein (CYP4A11-F434S) with reduced ?-hydroxylation activity that has been associated with high blood pressure and resistance to the anti-hypertensive effects of some diuretics. This apparent deregulation, in conjunction with decreased 20-HETE activity in the F434S variant, suggests that other unknown factors may contribute to the pro- and anti-hypertensive effects of CYP4A11. The central hypothesis is that expression and/or posttranslational modification differentially effects genetic variants of CYP4A11 with regard to 20-HETE synthesis and, ultimately, blood pressure control. CYP4A11 regulation and/or enzymatic activity will be tested for effects on 20-HETE levels and for influences by reactive oxygen species (ROS). A combination of biochemical, analytical, and enzymological tools will be used to further elucidate the differences between the CYP4A11 Phe-434 and Ser-434 variants in substrate selection, activity, and protein level. First, the use of chemoselective probes will determine the role of redox status in the posttranslational regulation in CYP4A11. Next, the relationship between CYP4A11 variant protein concentration and arachidonic acid metabolizing activity will be investigated in human microsomes and a transgenic mouse model. These experiments aim to further elucidate the role CYP4A11 variants play in hypertension. 20-HETE is an important component in hypertension. Genetic variations that alter its production cause significant changes in hypertension susceptibility and therapeutic response. Understanding the mechanisms related to the phenotypic variation in CYP4A11 will help to gain a more in-depth understanding of hypertension in different individuals and reshape how these specific persons are treated for blood pressure reduction.